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Modern variable speed drives with their fast rising voltage pulses and high switching
frequencies can generate current pulses that flow through the motor bearings,
which can gradually erode the bearing races and rolling elements.
The stress on motor insulation can be avoided by using optional ABB d
u
t
d
/d
filters also reduce bearing currents.
To avoid damage to motor bearings, the cables must be selected and installed
according to the instructions given in the hardware manual. In addition, insulated N-
end (non-driven end) bearings and output filters from ABB must be used according
to the following table. Two types of filters are used individually or in combinations:
•
u
t
optional d
/d
currents).
•
common mode filter (mainly reduces bearing currents).
filter (protects motor insulation system and reduces bearing
Planning the electrical installation 47
u
t
/d
filters.
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